The objective of this three year proposal is to continue development and application of enhanced serological and virological tests for detection of simian type D retrovirus (SRV/D) infection in macaques, and to evaluate the potential role of recombinant vaccines in a comprehensive strategy for SRV/D control and eradication. We propose to continue our development of the polymerase chain reaction (PCR) as a diagnostic tool for SRV/D detection using both "generic" and virus type-specific primers and probes. The potential of PCR to replace more expensive and time consuming viral isolation methods will be evaluated by direct comparison of antibody detection, virus isolation and PCR in clinical specimens. The generic and type specific capabilities o various sets of primers and probes will be validated against known SRV/D serotypes, as well as against uncharacterised field isolates. In addition, we will develop and utilize "second generation" immunoassays for SRV/D antibody detection using recombinant viral proteins and synthetic peptides, with the objective of bringing on-line diagnostic assays with increased sensitivity and specificity. Tests with increased sensitivity are needed to streamline testing algorithms, and to reduce the frequency of "indeterminate" results. The performance of these recombinant assays will be compared with current assays that utilize disrupted whole virus as target antigen, against an extensive panel of well characterized antisera (positive, negative and indeterminate). Once developed and validated, PCR and recombinant antibody assays will be applied to screening and surveillance for development and maintenance of SPF breeding colonies of macaques. The use of improved diagnostic methods in testing strategies could potentially accelerate the rate of SPF colony development significantly. There is evidence that SRV/D infection in macaques is "vaccine preventable", yet the use of vaccines as part of an over-all program of control and eradication has not, to date, been given serious consideration. We propose to extend previous studies to answer some existing questions regarding vaccine efficacy directly relevant to their potential role in infection control strategies. Two major question will be addressed, 1) are these recombinant vaccines protective under conditions of natural exposure? 2) do these vaccines protect against establishment of latent infections? To achieve these objectives we will carry out a vaccine trial by housing immunized and sham immunized juvenile rhesus macaques together with infecteds, as a group in a corn-crib, essentially recreating the type of situation where SRV/D is most highly infectious. The vaccine efficacy will be determined by clinical, virological and serological monitoring, including PCR. An efficacious vaccine could prove to be a valuable adjunct to serological and virological screening programs in the control of SRD/D in macaques.